1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device for preventing wet out.
2. Discussion of the Related Art
A cathode ray tube (CRT) is one of display devices generally used mainly for monitors of televisions (TVs), measuring instruments, information devices, etc. However, the heavy weight and a great bulk of the CRT, it is difficult to use while responding to the demand for miniaturization and light-weight of electronic products.
Therefore, the CRT has some limitations in the weight or size for the miniaturization and light-weight of various electronic products of current trend. To replace the CRT, LCDs (liquid crystal display devices) using electro-optical effect, PDPs (Plasma Display Panel) using gas discharge, and ELDs (Electro Luminescence Display) using electro luminescent effect have been suggested. Among these, LCDs are under active research.
Recently, the LCDs, which have the advantages of miniaturization, light-weight, and low power consumption to substitute the CRT have been developed to serve as a flat display device. The LCDs are used for monitors of desktop computers and large information display devices, in addition to laptop computers. Thus, the demand for the LCDs is continuously increasing.
Meanwhile, a touch panel is one of computer peripheral devices for inputting readily determined information into a computer by pressing a touch panel on the display surfaces of image display devices such as cathode-ray tubes (CRTs), liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and electro luminescence displays (ELDs).
Front and rear surfaces of an LCD have a front polarizer and a rear polarizer attached thereon, respectively. Haze, among the characteristics of the front and rear polarizers, represents a degree of light transmittance and scattering of the reflected light. When the haze is low, a difference in the screen brightness at the areas for blocking light such as black matrix or wirings is great, thereby causing unsmooth images. On the other hand, when the haze is high, the resolution is reduced.
FIG. 1 is a simplified perspective view illustrating a general liquid crystal display device.
As shown in FIG. 1, the liquid crystal display device comprises a liquid crystal display panel 30 for displaying images, a fluorescent lamp 31 for generating light, a lamp housing 32 in U-shape for covering the fluorescent lamp 31, a light diffusion plate 35, a first prism sheet 37, and a second prism sheet 36 layered on one surface of the liquid crystal display panel 30 in this order, a protective sheet 38, a light guide plate 33, and a reflective plate 34.
The liquid crystal display device further comprises a support main 39 for organizing and fixing the liquid crystal display panel 30 and a backlight unit.
Here, the fluorescent lamp 31, lamp housing 32, light diffusion plate 35, first and second prism sheets 37 and 36, protective sheet 38, light guide plate 33, and reflective plate 34 are referred to as the backlight unit.
The backlight unit functions to emit light to a display region A of the liquid crystal display panel 30. The display region A, not shown in FIG. 1, comprises two transparent plates attached with polarizers at the exterior surfaces, and a liquid crystal interposed between the inner surfaces of the two transparent plates.
Further, the liquid crystal display device comprises a driving circuit 40 for driving the display region A.
Although not shown in FIG. 1, the liquid crystal display device having the above constitutions is further equipped with a cover bottom for covering a lower surface and one side surface of the support main 39, and a case top for covering the edges of the liquid crystal display panel 30 and the cover bottom.
Further, the liquid crystal display device comprises a touch panel (not shown) on the top of the liquid crystal display panel 30. Both edges of the touch panel are fixed to the case top.
The liquid crystal display device also comprises an upper and lower polyerizers formed on top and bottom of the liquid crystal display panel 30, respectively.
FIG. 2 is a cross-sectional view illustrating a liquid crystal display device combined with a touch panel according to a conventional art.
As shown in FIG. 2, the liquid crystal display device comprises a support main 2, a backlight unit and a liquid crystal display panel 10 laminated inside the support main 2, a cover bottom 14 for covering a lower surface and one side surface of the support main 2, a case top 16 for covering the edges of the liquid crystal display panel 10 and the cover bottom 14, a touch panel 26 formed on the liquid crystal display panel 10 and fixed to the edges of the case top 16 using a double sided tape 27, and a protective film 28 formed on the touch panel 26.
Here, the support main 2 is a mold product molded to have a step-shaped projection surface at the inner surface. The very lower layer inside the support main 2 is installed with the backlight unit, and the liquid crystal display panel 10 is formed on the backlight unit.
The liquid crystal display panel 10 is equipped with a lower substrate 10b for forming switch devices (TFT), and an upper substrate 10a for forming color filters.
Here, a liquid crystal is interposed between the lower substrate 10b and upper substrate 10a. 
Top and bottom surfaces of the liquid crystal display panel 10 are installed with polarizers 22 and 24. The lower polarizer 22 formed on the bottom surface of the liquid crystal display panel 10 polarizes light beam supplied from the backlight unit and provides the polarized light beam to the liquid crystal display panel 10.
The upper polarizer 24 formed on the top surface of the liquid crystal display panel 10 polarizes the light beam supplied from the liquid crystal display panel 10 and emits the polarized light beam to the outside.
The cover bottom 14 is installed to cover a lower surface and one side surface of the support main 2. The case top 16 is installed to cover the upper surface and side surfaces of the support main 2 to fix the support main 2 and the liquid crystal display panel 10 together.
The backlight unit comprises a lamp housing 18 equipped with a light source 20, a light guide plate 6 for altering incident light from the light source 20 to a surface light source, optical sheets 12 formed on the light guide plate 6 for increasing efficiency of light that transmits into the liquid crystal display panel 10, and a reflective plate 4 formed on the lower surface of the light guide plate 6 for reflecting light emitted to the rear surface of the light guide plate 6 back into the liquid crystal display panel 10.
The light source 20 supplies predetermined light, which corresponds with power supplied from an exterior power unit, toward the light guide plate 6. Light from the light source emitted to the opposite side of the light guide plate 6 is reflected at the lamp housing 18, and then retransmitted into the light guide plate 6.
The light guide plate 6 distributes the light, incident from the light source 20, uniformly in the entire region thereof. That is, the light guide plate 6 uniformly distributes the incident light from the light source 20 to allow uniform light be transmitted into the liquid crystal display panel 10.
The reflective plate 4 reflects light incident from the lower surface of the light guide plate 6. That is to say, the reflective plate 4 reflects light incident from the light guide plate 6 so as to provide the incident light to the liquid crystal display panel 10.
The optical sheets 12 comprise upper/lower light diffusion sheets and upper/lower prism sheets. The optical sheets 12 diffuse light incident from the light guide plate 6 to distribute the light uniformly on the entire surface of the light guide plate 6.
Further, the optical sheets 12 increase a surface brightness by refracting and condensing the diffused light and diffuse light to widen a viewing angle.
The touch panel 26 is formed on the top surface of the liquid crystal display panel 10 cased by the case top 16 and the cover bottom 14.
Further, the double sided tape 27 is used to combine the touch panel 26 on the liquid crystal display panel 10.
The touch panel 26 is placed on the upper substrate 10a of the liquid crystal display panel 10 using the double sided tape 27 adhered on the top surface of the case top 16. The touch panel 26 is pressed with a stylus pen or a finger at the display screen projected from the liquid crystal display panel 10 to generate and detect corresponding positional signals.
In the conventional liquid crystal display device, the upper polarizer 24 is made of a hard coating film, and the lower polarizer 22 is made of an anti-glare 25% or a clear type film.